A cylinder lock includes a cylindrical-shaped cylinder case, a plug which has a keyhole opened at the front surface thereof and can be rotatably inserted into the inner peripheral surface of the cylinder case, and a plurality of tumblers which are disposed in such a manner as to be able to appear from and disappear into the outer peripheral surface of the plug and also which are energized in a direction where they can be engaged with the inner peripheral surface of the cylinder case to thereby prevent the rotation of the plug.
In a key plate which locks and unlocks the cylinder lock, there are provided cord grooves which, when the key plate is inserted into the keyhole completely, are able to match the respective tumblers to the outer peripheral surface (shear line) of the plug.
Now, FIG. 11 is a view explaining the relation between tumblers T, T' stored into the plug of the cylinder lock and a key plate K which, when it is inserted into the keyhole, presses against the tumblers T, T'.
There are provided a plurality of tumbler insertion holes along the longitudinal direction of the plug; and, into the respective tumbler insertion hole, there are inserted a tumbler T shown by a solid line and a tumbler T' shown by a chained line, opposite to the tumbler T in the vertical direction.
In the outer surfaces of the tumblers T and T' on the right side thereof, there is provided a cutaway recess 1, while a spring 2 is inserted into the cutaway recess 1.
A leading end portion 3 of the tumbler T projects upwardly from the outer peripheral surface of the plug and is engaged with the inner peripheral surface of the cylinder case, whereas a leading end portion 3' of the tumbler T' projects downwardly from the outer peripheral surface of the plug and is engaged with the inner peripheral surface of the cylinder case, to thereby preventing rotation of the plug.
In the respective interior portions of the tumblers T and T', there are formed key insertion holes 4 and 4' which respectively communicate with the keyhole of the plug; and, on the respective right inner wall surfaces of the key insertion holes 4 and 4', there are projectingly provided cord projections 5 and 5' respectively having heights corresponding to cords.
In the key plate K, there are formed two cord grooves: that is, a cord groove 6 which, when the key plate K is inserted into the keyhole completely, presses against the cord projection 5 downwardly to thereby match the leading end portion 3 of the tumbler T to the outer peripheral surface (shear line) of the plug; and, a cord groove 7 which, when the key plate K is inserted into the keyhole of the plug completely, presses against the cord projection 5' upwardly to thereby match the leading end portion 3' of the tumbler T' to the shear line of the plug.
Now, FIG. 12 is a front view of the key plate K, and there are provided the cord grooves 6 and 7 on the flat surface of a keyhole insertion portion 9 provided in such a manner as to extend from a leading end portion of a grip portion 8.
The cord groove 6 is used to push a plurality of the tumblers T including cord projections 5 having different heights down to their respective engagement removal positions, whereas the cord groove 7 is used to push a plurality of the tumblers T' including cord projections 5' having different heights up to their respective engagement removal positions. The cord grooves 6 and 7 are respectively formed in special shapes, and the positions of the cord grooves 6 and 7 that correspond to the cord projections 5 and 5' are requested with high positional precision because the tumblers T and T' must be matched to the shear line of the plug.
Accordingly, in cutting work of the cord grooves 6 and 7, there is used a profile milling machine (see Japanese Patent Unexamined Publication No. 4-19007 of Heisei) or an NC milling machine.
To work the cord grooves 6 and 7, the key plate K is clamped to a mounting member which is fastened and fixed onto a table of a milling machine, and while rotating a milling cutter of an end mill type positioned in front of the keyhole insertion portion 9, the table is fed to thereby start the cutting work from the front end of the keyhole insertion portion 9. When the milling cutter completes the cutting work to the rear end portion of one cord groove, the milling cutter is passed through the side surface of the keyhole insertion portion 9, to thereby escape outwardly thereof, and the table is then fed in a direction where the milling cutter can be returned to a position in front of the keyhole insertion portion 9. Next, the other cord groove 7 is worked similarly to the above-mentioned procedure.
However, in the above-mentioned key plate including the cord grooves, there are left problems to be solved which are as follows:
(1) When the cord groove is worked in one operation by an end mill having a diameter substantially equal to the width of the cord groove, the dimensional precision of the groove is generally liable to lower.
On the other hand, when the cord groove is worked in two operations by an end mill having a diameter smaller than the width of the cord groove, the dimensional precision and required surface roughness of the groove are liable to be secured. However, the time necessary to work the cord groove is doubled, to thereby result in the poor working efficiency.
(2) Even if the cord grooves are working in one operation, when the above working method of the cord grooves is analyzed, there are five required steps: (a) positioning the original point of the table with respect to the milling cutter; (b) working one cord groove while feeding the table; (c) feeding the table so as to escape the milling cutter and return it back to the position before working; (d) similarly to the step (b), working the other cord groove; and, (e) feeding the table so as to escape the milling cutter and return it back to the position before working.
Among the five steps, the steps (c) and (e) are wasteful steps which have no relation to the working of the cord grooves directly.
(3) In order to enhance the burglarproof effect, there is a case in which, separately from the tumblers, a dog plate is engaged with the cylinder case. However, if the dog plate is provided additionally, it is necessary to work a dog plate storage groove additionally on the flat surface of the key plate.
The present invention aims at solving the above problems, and it is an object of the invention to provide a key plate which not only can shorten the time necessary to work cord grooves and enhance the working precision of the cord grooves but also, when it is applied to a cylinder lock including a dog plate, can save the labor and time to work a dog plate storage groove.